The invention relates to an apparatus and a method for comminuting polycrystalline silicon.
Polycrystalline silicon is extracted by thermal decomposition of silicon compounds, such as, for instance, trichlorosilane, in a so-called Siemens reactor and accrues in the form of polycrystalline rods.
For the creation of single crystals by means of crucible pulling, the polycrystalline rods must firstly be comminuted into fragments. For applications in the solar industry also, the grown polycrystalline rods must firstly be comminuted into fragments.
In the prior art, various methods for the comminution of silicon rods are known.
U.S. Pat. No. 5,660,335 A discloses a comminution method in which a high-pressure water jet is fired onto a crystal rod.
In U.S. Pat. No. 6,360,755 B1 a method is described in which a crystal rod is comminuted with the aid of shock waves, generated by electrical energy.
In U.S. Pat. No. 4,871,117 A it is proposed to firstly decompact a crystal rod by heat action and then to comminute it by mechanical force action.
U.S. 2010/025060 A1 describes a crushing tool, comprising a drive means for a pneumatic piston, for guiding the piston installed in a housing from a retraction position to a projection position by means of air pressure, a guide tube, connected to the housing and extending in the motional direction of the piston, and a hammer head.
The rear end portion of the hammer head is inserted movably in the front end portion of the guide tube. When the piston is moved out of the retraction position into the projection position, the front end of the piston collides with the rear end of the hammer head.
U.S. Pat. No. 7,360,727 B2 discloses a mechanical crushing apparatus for comminuting a polycrystalline silicon rod, which apparatus comprises a base, as well as comminuting tools and mating tools, wherein comminuting tools and mating tools possess a longitudinal axis which is oriented at right angles to the longitudinal axis of the base and parallel to the surface of the base, and comminuting tools and mating tools are movable in such a way that a silicon rod to be comminuted, lying on the surface of the base, can be adjusted between the tools in such a way that all tools in the region of the silicon rod have contact with the silicon rod and the comminuting tools in front of and behind the silicon rod can be moved in the direction of their longitudinal axis up to a safety distance to the mating tool, and the comminuting tools, by means of a strike motion in the direction of their longitudinal axis, act on the silicon rod and shatter it.
Similarly, U.S. Pat. No. 7,360,727 B2 discloses a method for mechanically comminuting a polycrystalline silicon rod, in which the polycrystalline silicon rod is located on a height-adjustable base and is adjusted there between comminuting tool and mating tools in such a way that all tools in the region of the silicon rod have contact with the silicon rod, and comminuting tools and mating tools in front of or behind the silicon rod are brought closer together up to a safety distance and subsequently, in respect of all comminuting tools bearing against the silicon rod, a recurring striking momentum is started, which striking momentum effects a comminution of the silicon rod.
U.S. 2011/068206 A1 describes a crusher for efficiently comminuting a silicon lump, wherein a small amount of fine crushed material (powder) is formed. The crushing tool comprises a hammer head connected to a piston, wherein the hammer head is located without compressed air in a rest position and, through the use of compressed air, is moved from the rest position to collide with a silicon lump. In the crusher, a multiplicity of mutually spaced crushing tools, each having a hammer head, face the silicon lump present on a base.
It has been shown that, with the method known in the prior art, an optimal crushing result is unattainable. Too much energy, or a large number of recurring strikes, is necessary to comminute the silicon. This has negative effects on the contamination of the silicon. Moreover, the service life of the components used is unsatisfactory.
The object of the present invention has been defined on the basis of the above problems.